Search Results for thermal emf curves

This article provides an in-depth review of thermocouples and the metals from which they are made. It explains how dissimilar metal conductors in contact at opposite ends can generate an electromotive force if the junctions are heated or cooled to different temperatures. The article discusses thermocouple circuits and instrumentation, calibration methods, insulation requirements, operating ranges, measurement errors, and maintenance procedures. It also provides property data and emf curves for common metals and thermocouple types, and contains information on color coding used around the world.

Electromagnetic problem solutions are based on the macroscopic theory of the continuous model for the electromagnetic field (EMF). It is described by a system of integral or partial differential equations for five vector quantities, namely, electric field strength, electric flux density, current density, magnetic field strength, and magnetic flux density. This article describes the behavior of the EMF by Maxwell's equations in integral or differential forms. It discusses the definition of potentials; methods of mathematical modeling; boundary conditions; and energy, power density, and electromagnetic forces.

Temperature control in heat treating is of paramount importance in maintaining the quality and achieving the desired metallurgical results. This article provides a detailed account of the factors affecting temperature control in heat treating furnaces, with information on temperature control systems, including contact sensors, noncontact sensors, controllers, energy-flow regulators, measurement instruments, and set-point programmers. Common contact sensors include temperature scales, thermocouples, and resistance temperature detectors, whereas optical pyrometers and on-line radiation thermometers fall under the noncontact type. The article describes two types of instrumentation used in heat treating: field test instruments for temperature-uniformity surveys and system-accuracy tests; and controlling, monitoring, and recording instruments for digital instrumentation.

Induction heating is a combination of several interrelated physical phenomena, including heat transfer, electromagnetics, and metallurgy. This article presents a brief review of different heat transfer modes, namely, heat conduction, thermal radiation, and convection. It focuses on the specifics of induction heating and heat treating applications. The article discusses the nonlinear and interrelated nature of a particular heat transfer phenomenon, physical property, and skin effect. It also presents simple case studies and general physical laws governing different heat transfer modes. The article also discusses the basic concepts of direct current and alternating current circuits, and reviews the theory of electromagnetic fields.

This article describes the fracture mechanics in fatigue. It discusses the fatigue crack growth rate (FCGR) testing that consists of several steps, beginning with selecting the specimen size, geometry, and crack length measurement technique. The two major aspects of FCGR test analysis are to ensure suitability of the test data and to calculate growth rates from the data. The article presents an analysis of the crack growth data. Optical, compliance, and electric potential difference are the most common laboratory techniques, and the article reviews their merits and limitations. Forced-displacement, forced-vibration, rotational-bending, resonance, and servomechanical systems for various loading conditions are also discussed.

Testing and characterization of fatigue crack growth are used extensively to predict the rate at which subcritical cracks grow due to fatigue loading. ASTM standard E 647 is the accepted guideline for fatigue crack growth testing (FCGR) and is applicable to a wide variety of materials and growth rates. The two most widely used types of specimens are the middle-crack tension and compact-type specimens. This article describes the factors affecting the selection of appropriate geometries of these specimens: consideration of material availability and raw form, desired loading condition, and equipment limitations. Various crack measurement techniques, including optical, ultrasonic, acoustic emission, electrical, and compliance methods, are also reviewed. The article discusses the two major aspects of FCGR test analysis: to ensure suitability of the test data and to calculate growth rates from the data.

Designing of induction heating, or, generally electro technological installations, requires mathematical modeling for solving problems related to various physical phenomena, including electromagnetic (EM), thermal, mechanical, fluidic, and metallurgical fields. This article focuses on the solution of Maxwell's equations (MEs) and provides some basic information regarding the heat transfer and fluid equations, because these physical phenomena usually are strongly coupled to magnetic and electric fields. The solutions are usually obtained by using specific numerical methods such as finite-element method, finite difference method, boundary-element method or volume-integral method, and direct-solution method. The article also discusses the typical structure of commercial codes (preprocessor, solver, and postprocessor) to solve field problems mainly in finite-element method.

Electrical resistance alloys include those types used in instruments, control equipment, heating elements, and devices that convert heat generated to mechanical energy. This article discusses the basic classification of electrical resistance alloys (resistance alloys, heating alloys, and thermostat metals), their subtypes, properties, service life, and operating temperatures. It describes the designing and fabrication of open resistance and sheathed heaters. The article contains a collection of tables and graphs that provide information on the mechanical properties, chemical composition, temperature coefficient of resistance, furnace operating temperatures, length and spacing of loops, ribbon size, and electrical capacity of heating elements.

In this article, a metallurgical overview of the hardening process is provided. This overview is followed by the methodology involved in obtaining cooling curves, the currently accepted standardized methods of testing, and the use of newer methods of cooling curve data interpretation that describe the quenching process.

Induction hardening of steel components is the most common application of induction heat treatment of steel. This article provides a detailed account of electromagnetic and thermal aspects of metallurgy of induction hardening of steels. It describes induction hardening techniques, namely, scan hardening, progressive hardening, single-shot hardening, and static hardening. The article discusses the techniques used to control the heat pattern, and provides a brief review of quenching techniques used in the induction hardening. It provides guidelines for selecting the frequency and power for induction hardening, and describes common methods for measuring case depth, such as optical and microhardness, and surface hardness. It provides information on some complications and ambiguities associated with these measurements. The article also discusses the commonly used non-destructive testing methods, namely, magnetic particle testing, ultrasonic testing, and eddy current testing to evaluate induction-hardened components.

This article discusses the various factors that affect the corrosion performance of electroplated coatings. It describes the effects of environment and the deposition process on substrate coatings. The article provides a discussion on the electrochemical techniques capable of predicting the corrosion performance of a plated part. It reviews the designs of coating systems for optimal protection of the substrate. The article also discusses controlled weathering tests and accelerated tests used to predict and determine the relative durability of the coating.

Analysis of the failure of a metal structure or part usually requires identification of the type of failure. Failure can occur by one or more of several mechanisms, including surface damage (such as corrosion or wear), elastic or plastic distortion, and fracture. This leads to a wide range of failures, including fatigue failure, distortion failure, wear failure, corrosion failure, stress-corrosion cracking, liquid-metal embrittlement, hydrogen-damage failure, corrosion-fatigue failure, and elevated-temperature failure. This article describes the classification of fractures on a macroscopic scale as ductile fractures, brittle fractures, fatigue fractures, and fractures resulting from the combined effects of stress and environment.

This article discusses the general formability considerations of aluminum alloys. To conduct a complete analysis of a formed part, the required mechanical properties, as determined by several standard tests, must be considered. The article describes tension testing and other tests designed to simulate various production forming processes, including cup tests and bend tests, which help in determining these properties. It provides information on the equipment and tools, which are used in the forming of aluminum alloys. The article presents a list of lubricants that are most widely used in the forming. It also analyzes the various forming processes of aluminum alloys. The processes include blanking and piercing, bending, press-brake forming, contour roll forming, deep drawing, spinning, stretch forming, rubber-pad forming, warm forming, superplastic forming, explosive forming, electrohydraulic forming, electromagnetic forming, hydraulic forming, shot peening, and drop hammer forming.

Electrical resistance alloys used to control or regulate electrical properties are called resistance alloys, and those used to generate heat are referred to as heating alloys. This article covers both alloy types, describing the construction and use of resistors as well as heating elements. It also discusses soldering and joining methods, sensitivity and stability factors, and various design coefficients. In addition, it provides a detailed account of the properties and applications of thermostat metals and discusses the design of resistance heaters and their operating ranges.

Magnetic flux controllers are materials other than the copper coil that are used in induction systems to alter the flow of the magnetic field. This article describes the effects of magnetic flux controllers on common coil styles, namely, outer diameter coils, inner diameter coils, and linear coils. It provides information on the role of magnetic flux controllers for whole-body and local area mass-heating applications, continuous induction tube welding, seam-annealing inductors, and various induction melting systems, namely, channel-type, crucible-type, and cold crucible systems. The article also describes the benefits of the flux controllers for induction heat treating processes such as single-shot and scanning.